This application claims benefit of Japanese Patent Application No. 2001-145302 filed on May 15, 2001, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to a lens barrel of a camera, and the like, in which the lens barrel has a plurality of lens frames moving in an optical axis direction and firmly couples the lens frames with each other.
2. Description of the Related Art
Conventionally, lens frames of a lens barrel used in cameras, and the like, are often coupled with each other through helicoid threads so that they relatively move in an optical axis direction smoothly.
As a conventional method of coupling lens frames by helicoid threads, Japanese Unexamined Patent Application Publication No. 58-118612, for example, discloses a technology for eliminating not only backlash in rear gap but also backlash in radial engagement by engaging a roller, which fits in a roller shaft, with the one side surface of a helicoid thread of one of lens frames.
In the lens barrel arranged as described above, when a user drops a camera by mistake or when some kind or another shock or hit is applied to the camera, there is a possibility that a large amount of force is applied to the coupling portion between the lens frames.
In this accident, when external force acts in a direction where respective helicoid threads, which are threaded to each other, are released, it is necessary to prevent the helicoid threads from being easily released from each other to keep the coupling between the respective lens frames.
However, the above example of the conventional art intends to eliminate the backlash in rear gap and in radial engagement and has not a function for preventing the release of threaded helicoid threads. That is, since the shape of the roller is formed according to the shape of one of the helicoid threads on which the roller is abutted, a problem arises in that the roller is also disengaged from the helicoid thread similarly to the portion of the other helicoid thread.
Accordingly, it is an object of the present invention, which was made in view of the above circumstances, to provide a lens barrel that couples lens frames with each other making use of helicoid threads and that can keep the lens frames in a firmly coupled state even if unintentional external force is applied to the lens barrel.
A lens barrel includes a first frame having a helicoid female thread and a second frame having a helicoid male thread that is threaded with the helicoid female thread, and a pin member is disposed in any one of the first frame and the second frame. The pin member fits in the helicoid thread that is threaded with the helicoid thread of the frame in which the pin member is disposed, has a sliding contact surface that comes into sliding contact with the flank surface of the helicoid thread in which the pin member fits, and has an edge, which can bite into the flank surface of the helicoid thread, at the end of the sliding contact surface thereof.
The above and other objects, features and advantages of the invention will become more clearly understood from the following description referring to the accompanying drawings.